PLC tab

PLC tab

For Bus Terminal Controllers (BC), special data exchange variables for fieldbus-based communication between PC and BC can be defined under PLC variables (see sample configuration of a Bus Terminal Controller).

The following tab, amongst others, appears when a BC is selected in the TwinCAT System Manager's tree view:

PLC Cycle Time

The small controller's reserved cycle time. During this period, no data will be sent by the BC to the fieldbus. 

Background Time

Time for the processing of the communication via the fieldbus (includes program download, debugging, etc.). 

PLC Var. Offs IN

Start offset of the data exchange variables in the input area of the BC process image

PLC Var. Offs OUT

Start offset of the data exchange variables in the output area of the BC process image

AMS Response during download

Can be disabled for older Bus Terminal Controllers (e.g. BC2000 and BC3100) for compatibility reasons. Newer bus controller firmware versions acknowledge the receipt of individual download sequences. This checkbox must therefore be activated (in all cases for BC9000).

Start with Configuration Error

Even if the configured BC9000 is not connected to the network, it is possible to start the TwinCAT system if this checkbox is enabled. 

Retain Data

Store Retain Data: Activates the support of remanent data in the Bus Terminal Controller.

Size: Size of the remanent marker area within the Bus Terminal Controller (%Mx0 ... %Mxyy).

K-bus update

Double Cycle: Activates execution of I/O cycles (K-bus update) within the BC station before and after each PLC cycle.
Before PLC: A K-bus update will be carried out before executing the PLC cycle.
After PLC: A K-bus update will be carried out after executing the PLC cycle.

Firmware Update (via COMx)

This function can be used to update the BC firmware.

Variable tab

After adding variables below the tree entry PLC Variables you will see the dialog for the selected variable on the right-hand side, as described in the Variables Information section.

Choose meaningful names for the data exchange variables, because they will be used as variable names in the local BC process image when Variable information is exported. After this you can link the data exchange variables with existing tasks.

Sample configuration of a Bus Terminal Controller

The image below shows both data exchange variables and fieldbus variables. The Bus Terminal Controller managed terminals 4 to 9 locally.